I have already a mesh, the markers have the estimated coordinates.
I created them by selecting a photo, right-click at wanted location, then add marker. After that in the markers section, I have done "filter photos by marker" to identify the markers on other photos (at least 6 photos).
I have the estimated coordinates. Since they are not GCP i don't have the source coordinates. As I can't check them, I can't get the estimated error. It has something to do with the project parameters, alignment or mesh.